1. National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, P. R. China
2. College of Biomedical Engineering, Sichuan University, Chengdu 610064, P. R. China
3. Department of Dermatology, West China Hospital, Sichuan University, 37 Guo Xue Xiang, Chengdu 610041, P. R. China